1. Field of the Invention
The present invention relates to an automation system and a method for assembling a workpiece, and more particularly to an automation system and a method for supplying and assembling a paired workpiece such as an LCD panel.
2. Description of the Related Art
The liquid crystal display (LCD) panel is made by assembling two substrates. Sealant is applied around edges of the two substrates to seal the two substrates, and liquid crystal material is injected between the two substrates. One of the two substrates is a color filter (CF) substrate on which are formed a red, green and blue color filter, in addition to a black matrix. The other substrate is a thin film transistor (TFT) substrate on which are formed a plurality of pixel electrodes and TFTs in pixel regions.
FIG. 1 shows a schematic diagram of a partial sectional view of a typical LCD panel. As shown in the drawing, the LCD panel includes a TFT substrate 10, a CF substrate 1, spacers 20, and a sealant 30. The TFT substrate 10 and the CF substrate 1 are maintained to have a predetermined gap therebetween by the spacers 20, and the sealant 30 hermetically joins the TFT substrate 10 and CF substrate 1.
A typical method for manufacturing the LCD having the paired TFT substrate 10 and CF substrate 1 will be described hereinafter.
FIG. 2 is a schematic perspective view of uncut TFT substrate 10 and CF substrate 1, each having a plurality of cells. In the conventional LCD manufacturing method, a plurality of cells are formed on each of the TFT substrate 10 and the CF substrate 1 to enhance productivity. In FIG. 2, the CF substrate 1 has six cells (1-6) and the TFT substrate 10 has six cells (11-16). Each cell of the CF substrate 1 corresponds to one cell of the TFT substrate 10 to form cell pairs. For example, the cell 12 of the TFT substrate 10 corresponds to the cell 1 of the CF substrate 1.
Two separate substrates 10 and 1 are assembled together and each cell pair is cut to produce an LCD panel. However, while manufacturing the uncut TFT substrate 10 and CF substrate 1, one or more cells may become detective. One defective cell comprising an LCD panel renders the entire LCD panel useless and to be discarded. Accordingly, the TFT substrate 10 and the CF substrate 1 are given a grade depending on which, if any, of the cells are defective. The TFT substrate 10 and the CF substrate 1 of the same grade are assembled together, thereby increasing productivity.
The grade is an indication of defects on the substrates 10 and 1, and varies according to the number and the location of the defective cells that the substrates 10 and 1 have. Since each of the TFT substrate 10 and the CF substrate 1 of FIG. 2 has six cells, there are total 64 possible grades (2.sup.6) for each substrate.
The grades are outlined in Table 1 below. Defects are indicated by X, while O indicates no defects.
TABLE 1 Cell Cell Grade 1 Cell 2 Cell 3 Cell 4 Cell 5 6 Pattern 0 O O O O O O OOOOOO 1 X O O O O O XOOOOO 2 O X O O O O OXOOOO 3 X X O O O O XXOOOO 4 O O X O O O OOXOOO 5 X O X O O O XOXOOO 6 O X X O O O OXXOOO 7 X X X O O O XXXOOO 8 O O O X O O OOOXOO 9 X O O X O O XOOXOO 10 O X O X O O OXOXOO 11 X X O X O O XXOXOO . . . . . . . . . . . . . . . . . . . . . . . . 60 O O X X X X OOXXXX 61 X O X X X X XOXXXX 62 O X X X X X OXXXXX 63 X X X X X X XXXXXX
As shown in Table 1 above, the total number of possible grades is 64. A substrate with no defects has a `OOOOOO` pattern and a grade of `0` and a substrate with all defective cells has a `XXXXXX` pattern and a grade of `63`.
As stated above, if one of the two cells forming an LCD panel is defective, the entire LCD panel must be discarded. So, for example, if the cell 1 of the CF substrate and the cell 15 of the TFT substrate are defective and these substrates are assembled, the LCD panel of the cell 12 and the cell 1 as well as the LCD panel of the cell 15 and the cell 6 should be discarded. Therefore, it is necessary to sort out the substrates according to a grade so that substrates having the same number and location of defective cells are assembled together in order to minimize the number of assembled LCD panels to be discarded.